Mechanical resonator

ABSTRACT

1,163,706. Electric timepieces. CENTRE ELECTRONIQUE HORLOGER S.A. March 1, 1968 [March 31, 1967], No.10041/68. Heading G3T. A mechanical resonator for a timepiece comprises two branches 1, 2 adapted to oscillate in phase opposition, each having at its free end a mass 5, 6 belonging to a transducer maintaining the vibrations of the resonator and each branch having a flexible part 12, 13 to allow displacement of the masses under the influence of gravity in order to reduce the charge in frequency of the resonator due to its change in orientation. The masses oscillate in the direction of the line 11 but are displaced in a direction having a component perpendicular to the line 11 depending on the orientation of the resonator. Members 7, 8 are provided for fine adjustment of the frequency of oscillation of the resonator. In a modification the resonator comprises two parallel straight arms each having at its free end an inwardly facing U-shaped arm positioned at right angles to the straight arms. The flexible part is provided by the curved portion of each U-shaped arm to the free ends of which the masses are secured.

Dec. 23, 1969 M. HET ZEL I 3,486,049

MECHANICAL RESONATOR Filed March 12, 1968 2 Sheets-Sheet 1 IN VENTOR Dec. 23, 1969 M. HETZVEL 3,486,049

' MECHANICAL RESONATOR Filed March 12, 1968 2 Sheets-Sheet 2 v INVENTDR MAX HETZEL.

HTT R VE/ S United States Patent 3,486,049 MECHANICAL RESONATOR Max Hetzel, Bienne, Switzerland, assignor to Centre Electronique Horloger S.A., Neuchatel, Switzerland, a Swiss company Filed Mar. 12, 1968, Ser. No. 712,509 Claims priority, application Switzerland, Mar. 31, 1967, 4,575/ 67 Int. Cl. H02k 33/00; G04c 3/00 US. Cl. 31025 4 Claims ABSTRACT OF THE DISCLOSURE The present invention concerns a mechanical resonator of the type comprising two branches oscillating in phase opposition and each havingat its free end a mass belonging to a tnansductor maintaining the vibrations of the resonator.

It is known that resonators of this kind, when they are used in time-pieces, have the disadvantage of being affected with an error, called position error, i.e. that the frequency of oscillation depends on the position of the resonator in relation to the direction of gravity. The result is that, in the case of a wrist watch for instance, the changes in orientation of the watch in relation to the vertical direction will necessarily produce an appreciable daily error.

The purpose of the invention is to reduce, and even to suppress, the position error of the known resonators of the type considered. The resonator according to the invention is characterized in that each of its branches comprises a flexible part in order to allow a displacement of these masses under the influence of gravity, along a direction having a component which is perpendicular to the direction of oscillation of the said masses, as a function of the position of the resonator inspace, in order to reduce the position error.

FIGURES 1, 2 and 3 of the appended drawing illustrate, by way of examples, a plan view of two embodiments and of a variant of the resonator according to the invention.

The resonator according to FIGURE 1 is formed by a metallic part comprising two branches, arcuate and symmetrical in this example, connetced by a middle part 3 by means of which the resonator is secured by screws on 'a support which may be the body of a watch. In 4 may be seen the holes provided for this purpose in the part 3.

The branches 1 and 2 are arranged to oscillate in phase opposition and each comprises, at their free ends, masses 5 and 6, respectively, belonging to an electro-magnetic transductor of a known type ensuring the maintenance of the vibrations of the resonator. The coil of this transductor is not shown and it is well-known that it acts magnetically on the masses 5 and 6 in order to ensure, in conjunction with the elasticity of the branches 1 and 2, the periodic motion of the masses towards and away from one another.

In 7 and 8 may be seen two members for the fine adjustment of the frequency proper of the resonator, which are constituted, in a known manner, by eccentric rotary 3,486,049 Patented Dec. 23, I969 pieces. The frequency proper varies slightly with the angular position of these members.

The branches 1 and 2 oscillate owing to the flexion of the parts 9 and 10 of these branches adjacent 3 which are made thinner for this purpose.

The straight line 11 in dots and dashes illustrates the general direction of the oscillating motion of the masses 5 and 6 during the operation of the resonator.

In view of reducing and even eventually suppressing the position error of the resonator, the following arrangement is provided: each of the branches 1 and 2 comprises a flexible part, constituted in this example by thinned down parts 12 and 13, respectively, situated in the neighbourhood of the corresponding masses 5 and 6. These flexible parts 12 and 13 are provided to allow a slight displacement of the masses 5 and 6 under the influence of gravity, according to a direction which, in the illustrated example, is practically perpendicular to the direction 11 of oscillation of these masses. Besides it is suflicient if the direction of this displacement has a component which is perpendicular to the line 11.

It is easy to understand that, when the resonator is in a vertical position, the masses 5 and 6 being above and the middle part 3 below, the masses 5 and 6 under the influence of gravity move slightly downwards and so come closer to 3, owing to the flexion of the arms in 12 and 13.

If the resonator is placed vertically in the reverse position, i.e. with 5 and 6 below and 3 above, the masses 5 and 6 move on the contrary slightly away from 3, owing to the flexion in 12 and 13.

It can be proved that if the thinned down parts 12 and 13 are correctly dimensioned, in dependence of the masses 5 and 6, one obtains, thanks to the resilient flexion of the parts 12 and 13, an at least partial automatic correction of the position error of the resonator, and this for every possible position of the latter in relation to the vertical direction.

If the arms 1 and 2 are of uniform cross-section, the masses 5 and 6 do not quite oscillate in the direction of the line 11, this being due to the presence of the flexible parts 12 and 13. These masses oscillate along a direction which is oblique in relation to 11 and inclined towards the foot 3. The perturbating effect of this obliquity requires, in order that it may be compensated, the provision of a compensating mass distributed along the branches of the resonator, as may be seen in 14 and 1-5. These distributed compensating masses oscillate in directions forming an angle in relation to 11, but on the side opposite to the foot 3, i.e. to the direction of oscillation of the masses 5 and 6. It is easy to see that thus, by a judicious arrangement of the masses 14 and 15 the abovementioned perturbating eifect of the parts 12 and 13 may be compensated so as to obtain, finally, an oscillation of the masses '5 and 6 practically in the general direction 11. Thus the fixed part 3 of the resonator is practically subjected to no force of inertia which is not compensated by those of the other arm.

In a variant, the elastic parts 12 and 13 could obviously not be provided immediately adjacent the corresponding masses 5 and -6.

In the example according to FIGURE 2, the resonator comprises two symmetrical oscillating arms 16 and 17, called principal arms, an intermediate securing foot 18, and at the free ends of the arms 16 and 17, two U-shaped auxiliary arms 19 and 20, arranged symmetrically, in a direction perpendicular to the principal axis of symmetry 21 of the resonator.

The auxiliary arms 19 and 20 are integral, by one of their ends with the terminal part of one of the principal arms 16 and 17. On their other extremity, which is free, is secured a mass 22, respectively 23. The windings of the maintaining coils of the resonator, which act mag- 3 netically on the masses 22 and 23 are indicated schematically in 24 and 25.

It may be seen that the median resilient parts 26 and 27 of the auxiliary arms 19 and 20 allow a flexion of these arms which is similar to that which has been explained in the case of FIGURE 1 in relation to the resilient parts 12 and 13, ensuring in entirely similar fashion, the at least partial automatic compensation of the position error.

It is advantageous to provide that the centers of gravity G and G of the oscillating masses are situated at least approximately on the median lines 28, respectively 29 of the principal arms 16 and 17.

In the example according to FIGURE 2, the masses 22 and 23 are secured on one side (the side opposite the foot 18) of the auxiliary arms 19 and 20. In the variant according to FIGURE 3, the construction is improved by disposing the masses 22a and 23a in a symmetrical manner on the end of the auxiliary arms 19a and 20a.

In this manner the center of gravity G and G; of each of these masses is situated approximately at the intersection of the median lines 28a, respectively 29a, with the median line of the free ends of the auxiliary arms 19a and 20a.

I claim:

1. A mechanical resonator comprising two branches oscillating in phase opposition, said branches being connected together at one end and each having at its free end a mass belonging to a transductor maintaining the vibrations of the resonator, each of said branches comprising a resilient part allowing said masses to oscillate in the manner of unilaterally fixed prongs, and a flexible part in order to allow a displacement of these masses under the influence of gravity, along a direction having a component perpendicular to the direction of oscillation of said masses, said flexible part being dimensioned so as to reduce the position error with reference to a normal frequency of the oscillations.

2. A mechanical resonator according to claim 1 wherein each said branch comprises two flexible parts, one near the connection of said two branches, in order to ensure oscillation of said mass, and the other near said mass to allow the perpendicular displacement thereof.

3. A mechanical resonator as claimed in claim 1, wherein each of said oscillating masses is substantially divided into two partial masses by said flexible part of each branch and wherein each branch is curved and has its masses so distributed that the centers of gravity of said partial masses have components of oscillating motion parallel to an axis of symmetry of the resonator, the component of each partial mass being opposite to the component of the other mass of one branch in order to compensate the dynamic forces created by each one of said components in one branch.

4. A mechanical resonator according to claim 1, wherein said each branch is provided at its free end with an auxiliary resilient U-shaped arm, integral at one of its ends with the end of said branch, and bearing at its opposite free end one of the masses, said two auxiliary arms being arranged symmetrically in relation to the principal axis of symmetry of the resonator.

References Cited UNITED STATES PATENTS 3,170,278 2/1965 Stutz 310-25 XR 3,269,106 8/ 1966 Waldburger 58--23 3,283,495 11/1966 Hetzel et a1. 58--23 3,316,708 5/ 1967 Waldburger 5823 FOREIGN PATENTS 741,517 8/1966 Canada.

MILTON O. HIRSHFIELD, Primary Examiner B. A. REYNOLDS, Assistant Examiner U.S. Cl. X.R. 5823; 84409, 457 

